js 链式调用的实现原理

var doudou = {
	makeup: function () {
		console.log('I am beautiful!');
		return this;
	},
	eat: function () {
		console.log('I am strongger!');
		return this;
	},
	exercise: function () {
		console.log('I am younger!');
		return this;
	},
};
doudou.makeup().eat().exercise();